Why is my brain so awful towards me? Why can't I wrap my head around someone genuinely liking me for me?

Ok I wrote awhile back that I went out with someone who is different from the usual guys I chase after and have historically always been destroyed by. Things have been nothing short of fantastic with this guy and we are dating. I met his mother and from what I hear she likes me. He genuinely wants to see me win and always tries to build me up and I'm not used to it. He knows I've been struggling a lot lately at work and with my mental health and he's always offering to drop in or bring me stuff to cheer me up. He's always asking what he can do to help and I never know what to say. I feel bad for shooing him away but I don't want to be a burden and I don't want to come off as needy and demanding. I know I am difficult at times due to my anxiety and other mental health struggles but I also don't want to push him away either because he might think oh he doesn't want me around or he doesn't like me. It's not true but my stupid brain just does stuff like this.

He seriously caught me off guard last month after we had dinner out. He looked me dead in the eyes and said he genuinely cares about me and knows I can do so much more in life. He knows I am capable of so much more and he believes in me. I teared up because nobody in my entire life has told me anything like that. I could tell he meant it too because I could feel it in my bones. Someone as messed up as me doesn't deserve someone like him. He's too good for me I feel.

My friends are excited for me and say ooooh you're dating someone or oooooh you're in a relationship but my stupid self always denies it because to me we are just friends having dinner and going out. My stupid self can't comprehend someone liking me for me. My stupid self doesn't understand any of this. I really do like this guy but my idiot self just can't grasp the concept of someone genuinely liking me for me. I wish I could get it through my head, I wish I could accept that I do have someone special in my life. I wish I understood and am mad at myself for not being able to register it.